This invention relates to certain novel film-forming nitrileacrylate ester copolymers, and more particularly to aqueous latices of nitrile-acrylate ester copolymers and to a method of preparing said copolymers, films and latices.
Synthetic copolymers and interpolymers of monomer mixtures comprising acrylonitrile and acrylate esters are well known and some of them have well-established commercial utility. Particularly useful are the high acrylonitrile copolymers containing 80% by weight or more of acrylonitrile and the low acrylonitrile copolymers containing 20% by weight or less of acrylonitrile. The high acrylonitrile copolymers and interpolymers are most generally used in the manufacture of synthetic fibers and the low acrylonitrile copolymers and interpolymers are useful as elastomers. More details concerning the state of the art of the aforementioned acrylonitrile interpolymers may be found, for instance, in U.S. Pat. Nos. 2,412,034, 2,558,396, 2,688,608, and 2,958,670, as well as Industrial and Engineering Chemistry, vol. 47, pages 1000 et seq. (1955), vol. 46, pages 1992 et seq. (1954), vol. 43, pages 2500 et seq. (1951), Journal of the American Chemical Society, vol. 65, pages 2067 et seq. (1943), and Rubber Age, February 1953, pages 636-637.
It is well known that it is difficult to prepare films at normal temperatures from a latex resulting from the polymerization or copolymerization of high proportions of acrylonitrile as disclosed in U.S. Pat. No. 3,047,522.
U.S. Pat. Nos. 3,236,798 and 3,351,602 describe latices having a minimum film-forming temperature no greater than 25.degree. C. which comprise a copolymer containing from about 40 to 60 percent by weight of polymerized acrylonitrile. A copolymer is composed of a main polymer backbone or core of from about 70 to 95 percent by weight of polymerized acrylonitrile and from about 30 to 5 percent by weight of at least one other olefinically unsaturated monomer such as an acrylate ester which is copolymerizable with acrylonitrile, and said main polymer backbone or core is over polymerized with a major proportion of at least one acrylate ester such as, for example, ethyl acrylate. The latices described in these two patents exhibit a minimum film-forming temperature no greater than 25.degree. C., and the process for preparing such latices described in the two patents is a two-step process.